Phased array

About: Phased array is a research topic. Over the lifetime, 19428 publications have been published within this topic receiving 229231 citations. The topic is also known as: Phased Array Radar, PAR.

A photonic variable RF delay line for phased array antennas

Abstract: It is shown that by applying spatial frequency-dependent phase compensation in an optical heterodyne process a variable RF delay line can be synthesized over a prescribed frequency band. Experimental results which demonstrate the performance of the delay line with regard to both maximum delay and resolution over a broad bandwidth are presented. A spatially integrated optical system is proposed for control of phased array antennas. The integrated system provides mechanical stability essentially eliminates the drift problems associated with freespace optical systems, and can provide high-packing density. The approach uses a class of spatial light modulator known as a deformable mirror device and leads to a steerable arbitrary antenna radiation pattern of the true time-delay type. >

Broad-band fragmented aperture phased array element design using genetic algorithms

Abstract: In this paper, a synthesis procedure to design thin broad-band fragmented aperture array elements is described. The arrays are assumed to be infinite periodic and the elements consist of a conducting pattern etched on a dielectric backed by a groundplane. A genetic algorithm (GA) is used to design the conducting pattern, relative permittivity, and thickness of the dielectric substrate with respect to array scan and bandwidth performance. The fitness function in the GA is evaluated using a finite-difference time-domain code with periodic boundary conditions. For a substrate thicker than about 0.1 /spl lambda//sub L/ (/spl lambda//sub L/= wavelength at the lowest frequency in the frequency band investigated), it was found that a bandwidth of at least one octave can be obtained for arrays scanned within 45/spl deg/ from broadside.

Time multiplexed digital ultrasound beamformer

Abstract: A phased array digital ultrasound beamformer for use with an ultrasound transducer array. The beamformer includes a processing channel for each element of the transducer array. Each processing channel includes a digitizing circuit for converting the received signal to digital samples and a time multiplexed digital delay circuit responsive to delay coefficients for delaying the digital samples by time multiplexed delays to produce delayed, time multiplexed samples for forming two or more receive beams. The ultrasound beamformer further includes a summing circuit for summing the delayed, time multiplexed digital samples from each processing channel to form a stream of time multiplexed output samples that is simultaneously representative of two or more receive beams. A coefficient generator supplies the delay coefficients to the time multiplexed delay circuit in each of the processing channels.

Subarray configurations for digital beamforming with low sidelobes and adaptive interference suppression

Abstract: The paper investigates how subarrays in a large phased array should be arranged. The aim is to form sum and difference beams with low sidelobes with and without adaptation against external interference. At each array element phase shifting and amplitude tapering for one beam with low sidelobes is assumed. The other beams (e.g. difference beams) have to be formed digitally at the subarray outputs. Problems with grating lobes are considered.

The post-processing of ultrasonic array data using the total focusing method

Abstract: The use of ultrasonic arrays for NDT has increased significantly in recent years. This is due to the flexibility of array systems which can be electronically configured to produce plane, focused, steered and steer-focusedbeams. In this way, one array transducer can do the job of many standard single-element transducers. Currently, the approach is to have independently controlled parallel pulser-receiver channels connected to a number of array elements. These channels allow timing delays to be applied to each element on both transmission and reception. In this way a specific set of transmit-receive delays are applied to an array to create a specific beam profile. This paper describes an alternative approach in which the complete raw data set offline domain signals from every transmitter-receiver pair is collected, stored and post-processed. Theoretically, the time taken to acquire this data is approximately the same as that taken to perform a B-scan with the array. The key advantage is that post-processing of the complete raw data set enables any beam profile to be recreated. Additionally, this approach allows novel inspections to be performed which would be impossible with single-element transducers and impractical using the traditional phased array controller methodology. This paper concerns one such post-processing algorithm, the Total Focusing Method (TFM). In the TFM, an image is created in which the beam has been focused on every point within the field of view. This optimises the focusing performance of a given array. The use of the TFM is then demonstrated on a number of test structures and is proposed as a superior alternative to conventional array test techniques.